The invention relates to surveillance radar and the like, and, in particular, to means for controlling the number or rate of target reports applied to the signal processor of such a radar.
Surveillance radars frequently are used to detect targets on or over ocean surfaces and, for such purposes, may be ship-borne, air-borne or carried by a satellite. In such radars it is important to control the number or rate of target reports applied to its signal processor which, as is known, may operate as a threshold detector. One difficulty, however, is the fact that an excessive number of target reports saturates the signal processor. In particular, radar echoes from land, since they are of a relatively large cross section, frequently exceed the systems detection threshold and are reported as targets. Consequently, when operating near land, it is necessary to have some means of preventing the and echoes from reaching the signal processor and, of course, it is highly desirable to provide this means in a simple, inexpensive, straightforward and reliable manner.
It is, therefore, an important object of the invention to provide a simple and reliable land mass blanking circuit to prevent land echoes from reaching the signal processor of a surveillance-type radar.
More generally considered, an object of the invention is to provide range-responsive apparatus for selectively blanking the application of a series of relatively high strength video return signals to a gated radar signal processor.
Other specific objects will become apparent in the ensuing description.